Prof. Stefano Atzeni

Dipartimento di Energetica, Università di Roma

Time: 9:30 am, May 28, 2010

Place: Lecture Hall 111, Department of Physics

Abstract: In the next few years experiments will be performed first at the National Ignition Facility and then at laser MegaJoule with the aim of demonstrating thermonuclear ignition of inertially confined fuel. The above lasers deliver pulses of 1.5-2 MJ of UV light (with wavelength of 350 nm) in a few ns, with peak power of about 500 TW. The concept to be tested is based on indirect drive (i.e. compression of the fuel by X-rays generated and contained in a laser irradiated hohlraum) and central ignition of the fuel. The foreseen experiments rely on the knowledge acquired in about forty years of research in diverse areas such as laser-matter interaction, hydrodynamics, laser sciences, cryogenics, etc. Recent progress, however, has stimulated studies on the feasibility of ignition and substantial energy gain at smaller laser energy. This is the result of i) the introduction of schemes (such as fast ignition, and shock ignition) which separate the compression and ignition stages and relax symmetry requirements; ii) improved understanding of Rayleigh-Taylor instability and of techniques for reducing its growth, which make efficient direct-drive compression possible; iii) developments in laser technology, allowing for smoother beams, and for very high intensity PW beams.

In this talk I will briefly review the above developments, discuss the conditions required to achieve ignition using different schemes, and present a simple model (supported by simulations) to estimate target gain as a function of a small set of parameters. I will then discuss a few key open issues for the feasibility of these advanced schemes. Such topics are currently addressed within the HiPER (High Power Laser for Energy Research) project.